1. Field of the Invention
This invention relates to a portable spa which is lightweight, thermally insulated, and uses a minimum of energy to heat the water circulated therethrough. The spa hereof uses a heat generating member to frictionally generate heat by the flow of water therethrough, a novel tub construction which preserves the external appearance of the tub while utilizing economical foam insulation, and employs a lightweight hinged cover to allow a portion of the spa to remain covered during limited occupancy.
2. Description of the Prior Art
Heated, circulating water has long been recognized for its relaxing, therapeutic effects on bathers. Many resorts were established in the 1800's near natural hot springs where bathers gathered to relax. In recent years the use of "hot tubs", in-ground spas, and portable spas have enjoyed great popularity as the benefits of heated circulating water have been made more affordable for the average citizen.
Some of the spas now available to the public are sold as "portable" spas in that they are constructed above ground so as to require no plumbing and excavation and can be supported by an outdoor deck or the like. Such spas are portable in the sense that they can be moved, but are nonetheless quite heavy (usually in the range of 400 to 600 pounds) and may include water circulation equipment internal thereto which can be dislodged or loosened during movement. Others require high voltage (220 vAC) current to operate, which is not always conveniently located in the American home.
Because the water in the tub of the spa is to be heated to about 100.degree. to 105.degree. Fahrenheit, energy efficiency is a prime concern. To the extent that the rate of heat loss may be minimized through insulation, less energy need be expended in heating the water. To this end, spas have been insulated on the normally underneath side in an effort to retain as much heat as possible in the water in the tub. Such insulation is shown, for example in U.S. Pat. No. 4,843,659 to Popovich et al., which discloses a foamed plastic sheet wound in a spiral. Such a manufacturing process is relatively labor and material intensive.
Thermal loss may also be avoided on the top of the tub by placing a cover thereover. Covers have been developed for this purpose. For example, a 6 inch foam insulated cover is offered by Future Industries USA, Inc. of Wayne, N.J. . However, this cover is of unitary construction and must be completely removed when the tub is in use by even a single occupant. Accordingly, a need has developed for a spa cover which can cover at least part of the tub when the spa is not fully occupied.
Finally, during start-up and periodically thereafter, some means for heating the water circulating through the tub must be provided. These heating devices may include resistance heaters or even gas or wood fired units. U.S. Pat. No. 4,893,659 shows a heat scavenging coil which collects waste heat from the pump motor and transfers the heat to the circulating water. However, it has been found that while use of this waste heat is advantageous, this source alone is generally insufficient to rapidly and economically warm the water within the tub.
Accordingly, there has developed a need for a lightweight, economical, and energy-efficient portable spa which is practical to use and easy to manufacture.